Situations frequently occur in which there is a need for two parts to be securely connected together. As a typical example, attention may be directed to German utility model No 93 08 051.4 in which a container has side wall portions which are pivotable relative to the bottom of the container and which are provided with connecting means in order to connect the side wall portions together in their operative position and secure them in that position. For that purpose, the one side wall portion is provided at its end with at least one extension which engages into an opening in the other side wall portion to form the connection. In that assembly, arranged within the opening in the other side wall portion is a projection which extends substantially in the main plane of the opening and which, in the operative position of the portions, engages into an aperture disposed on the extension of the other portion of the container. That provides for a positively locking connection between the two portions which are to be connected together. In order to prevent unintentional disengagement of the connection between the two portions, that container also includes, between the side wall portions and/or between them and the bottom, a fixing device which exerts a biasing force operative in a direction such as to maintain the connection. To make the connection between the side wall portions of the container, the co-operating connecting elements are required to be elastically deformed, and that necessitates a certain level of skill. A certain amount of force also has to be applied to produce the elastic deformation effect. Furthermore, there is the risk, when external forces act on the container, for example in transportation thereof, that the biasing forces which are intended to maintain the portions in the connected condition might be overcome so that the connection is accidentally released.